The term "polyphenylene ether resin" includes a family of polymers well known to those skilled in the art and described in numerous publications including Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875. The high molecular weight polyphenylene ethers are high performance engineering thermoplastics possessing relatively high softening points and are useful for many commercial applications including films, fibers and molded articles.
As is common with other thermoplastic polymers, polyphenylene ethers undergo photodegradation from prolonged exposure to ultraviolet radiation. This photodegradation is exhibited by a change in color, more particularly, an increase in yellowness due to the formation of yellow color bodies on the surface. Their resistance to ultraviolet radiation can be increased significantly by addition of ultraviolet radiation absorbers. The use of ultraviolet radiation absorbers to provide protection against photodegradation in resins is known to the art. These ultraviolet radiation absorbers (UV absorbers) function by reason of their high absorptivity of damaging ultraviolet wavelengths relative to that of the polymer. Common UV absorbers include benzophenones and benzophenone derivatives, benzotriazoles and benzotriazole derivatives.
Although these UV absorbers provide adequate UV stability, the addition of these components is often accompanied with a loss of desired physical properties of the polyphenylene ethers and their blends. In particular, the heat distortion temperature is lowered to an unacceptable degree, resulting in a loss of dimensional stability.
The present invention overcomes these difficulties by incorporating UV absorbers onto the polyphenylene ether polymer. Therefore, separate additives which diminish the physical properties need not be introduced.